Sugar-recovery centrifuge



Dec. 6, 1966 w. DlETZEL ETAL SUGAR-RECOVERY CENTRIFUGE Filed June 16, 1965 INVENTORS WAL TER DIE TZE L HEINRICH HILL EBRA ND A itorney United States Patent f 3,290,172 SUGAR-RECOVERY CENTRIFUGE Walter Dietzel, Braunschweig, and Heinrich Hlllebrand, Supplingen, Germany, assignors to Braunschwelgische Maschinenbauanstalt, Braunschweig, Germany, a corporation of Germany Filed June 16, 1965, Ser. No. 464,532 Claims priority, application Germany, Oct. 2, 1962, B 69,045; Mar. 3, 1964, B 75,697 5 Claims. (Cl. 127-19) This application is a continuation-in-part of our copending application Ser. No. 294,692, filed July 12, 1963, now US. Patent No. 3,205,095.

In said application Ser. No. 294,692, as well as in our copending applicationSer. No. 239,741, filed November 23, 1962, now US. Patent No. 3,207,627, we have disclosed a sugar-recovering centrifuge comprising a drum with an upwardly diverging peripheral wall centered on a vertical axis of rotation, this wall being provided with perforations for the outward passage of liquid from a fluent mixture driven upwardly along the wall by a component of the centrifugal force acting thereon. The remaining solids (such as sugar crystals), migrating along the inner wall surface toward the upper rim of the drum, are driven across that rim into a receptacle therefor. In order to facilitate this migration, it is convenient-as likewise disclosed in the copending applicationsto spray or otherwise deposit a treatment liquid, such as water, on the fluent mass as a cover fluid therefor. This liquid may also serve as a treatment agent and, in particular, will help remove entrained carbon and other residue or as to be separated from the crystals.

In the more elaborate apparatus disclosed in our application Ser. No. 294,692, we have replaced the simple funnel-shaped centrifuge drum by a composite drum consisting of alternately inverted funnels disposed in coaxially nested relationship around the vertical axis of rotation and carried on a common supporting disk. The innermost funnel, again, has an upwardly diverging perforated peripheral wall and is separated by two intermediate imperforate funnels from the outermost funnel which also has peripheral perforations. Other walls spacedly surround the innermost and outermost funnels for intercepting the liquid issuing from their perforationsand directing it into a special compartment whence it may be recirculated or removed for other purposes. An annular gap separates the wider end of each inner drum from the adjacent narrower end of the next-outer drum to permit the migration of solids to the latter drum across the diverging rim of the former. The large annular clearances, of generally triangular cross section, present between successive funnels form spaces in which the fluent mass under treatment can freely expand, upon emerging from the aforesaid gap, for a thorough mixing of its liquid and solid phases before further axial acceleration and/or liquid separation. Thus, the solids and their cover liquid travel along a zig-zag path defined by the generatrices of the innermost and intermediate funnels until they reach the inner wall of the outermost funnel of the centrifuge, this arrangement resulting in a particularly compact construction while atfording an extended treatment path without objectionable confinement and resultant stratification of the mass in its travel along that path.

The provision of means for supplying additional liquid along the treatment path enables a device of this type to be used not only with mixtures of high fluidity but also with relatively concentrated syrups; a convenient point of introduction for the additional liquid, following the removal of most of the original mother liquor, is at an intermediate level between the median height and the wide upper end of the innermost funnel, e.'g. at approximately 3,290,172 Patented Dec. 6, 1966 two-thirds of its height as likewise shown in our application Ser. No. 294,692.

According to the disclosure of the latter application, the generatrices of the frustoconical drum walls may be inclined to the vertical at various angles, preferably angles ranging between 15 and 40.

Experience has shown, however, that the apparatus just described does not invariably operate as smoothly and efliciently as desired, especially in the treatment of highly concentrated syrups. We have now found, in accordance with a feature of our instant invention, that the angle of inclination of the generatrices with reference to the vertical should be maintained within a rather limited range, between substantially 30 and 35, at least insofar as the innermost and intermediate funnels are concerned (thus with the possible exception of the outermost, downwardly diverging funnel wall). In other words, the apex angle of each frustocone except, at most, the outermost one should lie in the range of approximately 60 to 70. With an obtuse or substantially right apex angle, even a single cone drum would have to be of impractically large diameter in order to accommodate the quantity of wash water required for such heavy solutions; with a zig-zag or interleaved funnel arrangement of the type described in application Ser. No. 294,692, of course, this drawback is greatly magnified; besides, the continuity of the crystalline layer may in such case be impaired by reason of the unmanageable centrifugal forces that would occur. Moreover, the quantity of additional liquid supplied or recirculated would be uneconomically great.

Our present invention, accordingly, realizes the important object of eliminating the drawbacks just referred to.

Centrifuge drums of the nested-funnel type, built with acute apex angles within the range specified above, are most effective when the length of the generatrices of each acute frustocone (thus of the innermost and intermediate funnels) ranges between substantially 180 and 250 mm, a preferred length being on the order of 20 cm.

The invention will be described hereinafter in greater detail with reference to the accompanying drawing whose sole figure illustrates, in axial cross-section, a sugarrecovering centrifuge embodying our present improvement.

The centrifuge 1 shown in the drawing is generally of the type disclosed in our copending application Ser. No. 294,692 and comprises a cylindrical housing 3 with a removable cover 3a, a centrifuge drum 9 in the housing rotatable about a vertical axis 0, and a motor 4 for driving the drum shaft 2 via a belt-type transmission 5. A cylindrical partition 17 within housing 3, fixedly secured thereto, has a floor 17a with a raised central platform 17b from which depends a bearing for the shaft 2. This shaft carries a hub 10a of a disk 10 supporting the drum 9; the latter is composed of an upwardly diverging innermost funnel 9a, a downwardly diverging first intermediate funnel 9b, an upwardly diverging second intermediate funnel 9c and an upwardly diverging outermost funnel 9d. The peripheral walls of funnels 9a and 9d are perforated at 22 and 23, respectively, those of funnels 9b and 9c being solid. Annular gaps 18a, 18b, 180, separate the larger ends of funnels 9a, 9b, 9c from the smaller ends of surrounding funnels 9b, 9c and 9d, respectively. The lower end of funnel 9b, resting on the disk 10, is formed with peripheral apertures 19 opening into the gap 18b.

A frustoconical 'wall 7, diverging downwardly, rigidly surrounds inner funnel 9a and opens into an annular molasses compartment 6 adapted to receive the mother liquor initially separated from a syrup introduced through an inlet 14 into a cup 20 at the bottom of central funnel 9a. Conduits 11, controlled by one or more valves 12, terminate near the inner wall surface of this funnel to deliver to the ascending mass a stream of treatment liquid (e.g. wash water) from a supply line 13; it will be noted that this stream is delivered at a point approximately one-third down along the frustoconical funnel wall from its wide upper base. The skirt 7 is attached to funnel 9a at a location above the outlets of conduits 11 in order to drain oif excessive liquid therefrom as it emerges from the perforations 22 of that funnel. The remainder of the mass passes through gap 18a onto the inner surface of funnel 9b, expanding in the clearance between funnels 9a and 9b as it emerges from the gap. It subsequently traverses the apertures 19 and the gap 18b whence it ascends the sloping wall of funnel 90 before moving through the gap 180 into contact with the inner wall surface of perforated outermost funnel 9d. Liquid squeezed out through the perforations 23 of the latter funnel is collected in an annular space 24, bounded by a frustoconical outer shield 28, and delivered by drain pipes 25 to a further collector chamber 8. Peripheral apertures 26 at the bottom of funnel 9d allow for the discharge of the remaining solids across a peripheral apron 10b of disk 10 into a sugar compartment 27. Drain pipes 15 and 16 extend from compartments 8 and 6, respectively, to carry off the liquids accumulated therein.

A further set of conduits 11' terminate near the upper rim of funnel 9c to deliver supplemental rinse water or other treatment fluid thereto from a supply line 13 and under the control of one or more valves 12'.

It will be noted that the generatrices of funnels 9a, 9b and 90 all include angles of approximately 32 with the vertical, i.e., with the drum axis these angles lie, accordingly, within the range of 30 to 35 proposed in accordance with this invention. The length of the generatrices referred to is on the order of 20 cm.

We claim:

1. A sugar-recovery centrifuge for the separation of solids from a liquid in a fluent mixture, comprising:

a housing;

:a centrifuge drum in said housing composed of a plurality of nested and alternately inverted funnels centered on a common vertical axis and including an upwardly diverging innermost funnel and a downwardly diverging outermost funnel, each of said funnels except at most said outermost funnel having a frustoconical wall with generatrices inclined to the said axis at an angle ranging between substantially 30 and 35 each funnel other than said outermost funnel having a wide end separated from an adjoining narrow end of the next-outer funnel by an annular gap enabling the migration of solids from its own inner wall surface to the inner wall surface of said next-outer funnel, at least said innermost and outermost funnels being provided with peripheral perforations for the outward passage of liquid separated from the migrating solids, the length of said generatrices ranging between substantially 180 and 250 mm.;

fluid supply means opening into at least said innermost funnel for delivering a treatment liquid to the inner wall surface thereof at an intermediate level between the wide and narrow ends of said innermost funnel;

wall means spacedly surrounding said innermost and outermost funnels for intercepting liquid issuing from said perforations;

and drive means for rotating said drum about said axis.

2. A sugar-recovery centrifuge for the separation of solids from a liquid in a fluent mixture, comprising:

a housing;

a centrifuge drum in said housing composed of a plurality of nested and alternately inverted funnels centered on a common vertical axis and including an upwardly diverging innermost funnel, a pair of intermediate funnels and a downwardly diverging outermost funnel, each of said innermost and intermediate funnels having a frustoconical wall with generatrices inclined to said axis at an angle ranging between substantially 30 and 35, each funnel other than said outermost funnel having a wide end separated from an adjoining narrow end of the nextouter funnel by an annular gap enabling the migration of solids from its own inner wall surface to the inner wall surface of said next-outer funnel, said innermost and outermost funnels being provided with peripheral perforations for the outward passage of liquid separated from the migrating solids, the length of said generatrices ranging between substantially and 250 mm.;

fluid supply means opening into at least said innermost funnel and one of said intermediate funnels for delivering .a treatment liquid to the inner wall surface thereof at an intermediate level between the wide and narrow ends of the respective funnel;

wall means spacedly surrounding said innermost and outermost funnels for intercepting liquid issuing from said perforations;

and drive means for rotating said drum about said axis.

3. A sugar-recovery centrifuge for the separation of solids from a liquid in a fluent mixture, comprising:

a housing;

a centrifuge drum in said housing composed of a plurality of nested and alternately inverted funnels centered on a common vertical axis and including an upwardly diverging innermost funnel, a pair of intermediate funnels and a downwardly diverging outermost funnel, each of said innermost and intermediate funnels having a frustoconical wall with generatrices inclined to said axis at an angle ranging between substantially 30 and 35, each funnel other than said outermost funnel having a wide end separated from an adjoining narrow end of the next-outer funnel by an annular gap enabling the migration of solids from its own inner wall surface to the inner wall surface of said next outer funnel, said intermediate funnels having solid walls, said innermost and outermost funnels being provided with peripheral perforations for the outward passage of liquid separated from the migrating solids, the length of said generatrices being substantially 180 and 250 mm.;

fluid-supply means opening into at least said innermost funnel and one of said intermediate funnels for delivering a treatment liquid to the inner wall surface thereof at an intermediate level between the wide and narrow ends of the respective funnel;

wall means spacedly surrounding'said innermost and outermost funnels for intercepting liquid issuing from said perforations;

and drive means for rotaing said drum about said axis.

4. A sugar-recovery centrifuge for the separation of solids from a liquid in a fluent mixture, comprising:

a housing;

a centrifuge drum in said housing composed of a plurality of nested and alternately inverted funnels centered on a common vertical axis and including an upwardly diverging innermost funnel and a downwardly diverging outermost funnel, each of said funnels except at most said outermost funnel having a frust'oconical wall with generatrices inclined to said axis at an angle ranging between substantially 30 and 35, each funnel other than said outermost funnel having a wide end separated from an adjoining narrow end of the next-outer funnel by an annular .gap enabling the migration of solids from its own inner wall surface to the inner wall surface of said next outer funnel, at least said innermost and outermost funnels being provided with peripheral perforations for the outward passage of liquid separated from the migrating solids;

fluid-supply means opening into at least said innermost funnel for delivering a treatment liquid to the inner wall surface thereof at an intermediate level between the median height and the wide end of said innermost funnel;

wall means spacedly surrounding said innermost and outermost funnels for intercepting liquid issuing from said perforations;

and drive means for rotating said drum about said axis.

5. A sugar-recovery centrifuge for the separation of solids from a liquid in a fluent mixture, comprising:

a housing;

a centrifuge drum in said housing composed of a plurality of nested and alternately inverted funnels centered on a common vertical axis and including an upwardly diverging innermost funnel and a downwardly diverging outermost funnel, each of said funnels except at most said outermost funnel having a frustoconical wall with generatrices inclined to said axis at an angle ranging between substantially 30 and 35, each funnel other than said outermost funnel having a wide end separated from an adjoin- 2 ing narrow end of the next-outer funnel by an annular gap enabling the migration of solids from its own inner wall surface to the inner wall surface of said next-outer funnel, said innermost and outermost funnels being provided with peripheral perforations for the outward passage of liquid separated from the migrating solids, the length of said generatrices ranging between substantially 180 and 250 mm.;

fluid-supply means opening into at least said innermost funnel and at least one further upwardly diverging funnel for delivering a treatment liquid to the inner wall surface thereof at an intermediate level between the median height and the wide end of said innermost funnel;

wall means spacedly surrounding said innermost and outermost funnels for intercepting liquid issuing from said perforations;

and drive means for rotating said drum about said axis.

References Cited by the Examiner UNITED STATES PATENTS 11/1937 Andrews.

9/1965 Dietzel et al. 127--19 

1. A SUGAR-RECOVERY CENTRIFUGE FOR THE SEPARATION OF SOLIDS FROM A LIQUID IN A FLUENT MIXTURE, COMPRISING: A HOUSING; A CENTRIFUGE DRUM IN SAID HOUSING COMPOSED OF A PLURALITY OF NESTED AND ALTERNALTELY INVERTED FUNNELS CENTERED ON A COMMON VERTICAL AXIS AND INCLUDING AN UPWARDLY DIVERGING INNERMOST FUNNEL AND A DOWNWARDLY DIVERGING OUTERMOST FUNNEL, EACH OF SAID FUNNELS EXEPT AT MOST SAID OUTERMOST FUNNEL HAVING A FRUSTOCONICAL WALL WITH GENERATRICES INCLINED TO THE SAID AXIS AT AN ANGLE RANGING BETWEEN SUBSTANTIALLY 30 AND 35*, EACH FUNNEL OTHER THAN SAID OUTERMOST FUNNEL HAVING A WIDE END SEPARATED FROM AN ADJOINING NARROW END OF THE NEXT-OUTER FUNNEL BY AN ANNULAR GAP ENABLING THE MIGRATION OF SOLIDS FROM ITS OWN INNER WALL SURFACE TO THE INNER WALL SURFACE OF SAID NEXT-OUTER FUNNEL, AT LEAST SAID INNERMOST AND OUTERMOST FUNNELS BEING PROVIDED WITH PERIPHERAL PERFORATIONS FOR THE OUTWARD PASSAGE OF LIQUID SEPARATED FROM THE MIGRATING SOLIDS, THE LENGTH OF SAID GENERATRICES RANGING BETWEEN SUBSTANTIALLY 180 AND 250 MM.; FLUID SUPPLY MEANNS OPENING INTO AT LEAST SAID INNERMOST FUNNEL FOR DELIVERING A TREATMENT LIQUID TO THE INNER WALL SURFACE THEREOF AT AN INTERMEDIATE LEVEL BETWEEN THE WIDE AND NARROW ENDS OF SAID INNERMOST FUNNEL; WALL MEANS SPACEDLY SURROUNDING SAID INNERMOST AND OUTERMOST FUNNELS FOR INTERCEPTING LIQUID ISSUING FROM SAID PERFORATIONS; AND DRIVE MEANS FOR ROTATING SAID DRUM ABOUT SAID AXIS. 